274 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
the mountain the rock appears as if massively bedded, with an east and west 
trend, and a 10° to 15° southward dip. Eastward from Eagle Mountain 
three or four miles the red granitic porphyries were again found exposed. 
On the foot of the mountain on the south, moderately coarse dark-gray ortho- 
clase-gabbro was in place, appearing to underlie the granitie porphyry. 
Leaving Eagle Mountain, the course of the party lay in a northerly 
direction, through a string of four lakes. In the second of these, Pike 
Lake, massive ledges of gray gabbro 10 to 30 feet high run along both 
sides of the lake. This gabbro is very coarse, much weathered and iron- 
stained, and shows a great deal of very coarse titaniferous magnetite. Under 
the microscope it is seen to be closely allied to the Duluth gabbros, from 
which it differs, however, in having more orthoclase, a less-altered diallage, 
and in containing quite a little secondary quartz. The same rock continues 
largely exposed to the end of the last Jake in the series in about what would 
be Sec. 15, T. 63, R. 2 W. From the last lake the trail leads through a 
gorge 10 miles in a direction slightly north of west to Brulé Lake. The 
walls of the gorge average some 50 feet in height, now and then rising into 
cones of bare rock 100 to 150 feet high. They are often not more than a 
few rods apart. That on the north is for most of the distance red granitic 
porphyry, and that on the south at first the coarse gray gabbro of the lakes 
below, while nearer Brulé Lake it is composed of a finer-grained brownish- 
gray orthoclase-gabbro. In this rock there is a good deal of augite with 
crystalline outlines, it having formed before the feldspars, besides diallage 
with the usual relation to the feldspars, which are both oligoclase and ortho- 
clase. There is contained a great deal of titaniferous magnetite in black 
rods. 
Brulé Lake is a sheet of water some ten miles in length by two in great- 
est width, with an exceedingly irregular outline, and numerous rocky islands. 
The lake lies in a rock basin, and its shores, especially the northern, rise 
into bold cliffs, and the whole landscape is unequalled for beauty anywhere 
in the Northwest. There was not enough time spent here to work out any 
details, but enough was seen to learn that the rocks lie in distinct belts 
trending slightly south of west. At the northwest corner a red granitic 
porphyry like that of Eagle Mountain has a great development. South 
